Train locomotives, such as diesel electric locomotives, used to move railway cars along a track are propelled by exerting torque to drive wheels associated with the locomotive that are in contact with rails of the track. The power to propel the locomotive is typically provided first as mechanical energy by a high horsepower diesel engine. The diesel engine drives a generator that converts the mechanical energy to electrical energy. The electrical energy is transferred to traction motors which convert the electrical energy back to mechanical energy in order to drive axles connected to the drive wheels. Friction between the drive wheels of the locomotive and the rails provide the traction for causing movement of the locomotive and the railway cars.
During operation, heat is generated by the engine. In order to prolong the life of the engine and its components, and to maintain efficiency, it is necessary to reduce the temperature of the components to an acceptable level by providing engine cooling. Therefore, all locomotives incorporate a cooling system for cooling the engine and its components.
In a locomotive engine, cooling of the engine components is usually provided by water cooling. The heat generated by the engine is transferred to water circulating through a cooling loop. A water pump provides the water circulation and transfers the heated water from the engine through the cooling loop to a radiator. The radiator typically includes a fan that drives ambient air through the radiator in order to transfer the heat of the water in the water loop to the surrounding air. The cooled water is then circulated to other engine components, such as an oil cooler, and then back to the engine to be reheated. The specific operation, as well as the different systems involved, in the above-described closed loop water cooling system is well known in the art.
Known water pumps for locomotives are typically centrifugal, impeller type water pumps that are mounted on the front-end cover of the engine. Such water pumps have a driving shaft that is operatively coupled to the free end of the crankshaft of the engine and is driven thereby. Traditional mechanically driven water pumps, however, continue to run even under certain conditions such as low load or part load engine conditions. This can lead to slow engine warm up and the degradation of seals due to prolonged operation at idle or lower notches, which ultimately limits water pump and engine life.
It may therefore be desirable to provide a cooling system that is different from existing systems.